In recent years the necessity for increased productivity of natural and synthetic gases for fuel and raw material for chemicals production has placed a strain on the existing acid-gas treating plants throughout the world. The need for greater capacity, increased sulfur removal and the processing of streams containing higher concentrations of acid gases has caused the industry to recognize the need for the ability to increase the concentration of the absorbent, i.e., alkanolamine. One consequence of operating acid-gas stripping plants under these conditions is that increased corrosion of the metal of construction of the plant occurs, particularly in the reboiler and associated piping of the regeneration portion of the plant. Therefore, a search for ways to reduce corrosion has been underway by both the absorbent media suppliers and the engineering firms who service this industry. A recent development in our laboratories has resulted in the discovery that the corrosion of acid-gas stripping plants can be inhibited by maintaining a concentration of copper and sulfur in the absorbent medium circulating through the plant. Laboratory work has correlated well with field experience relative to the inhibitory effect; but, experience has shown that much less inhibitor need be present than laboratory tests appeared to indicate. In fact it was discovered that laboratory experiments were indicative of ability of the inhibitors to passsivate new or severely corroded metals and that once passivation was achieved, much less inhibitor was necessary to maintain the passivation. In addition, pilot plant and field testing illustrated that techniques for on-line measuring of the corrosion were needed which would indicate corrosion condition onset prior to actual corrosion of the plant metals. Such an on line system would thus signal the need for greater concentration of inhibitors.
It is therefore the object of the present invention to provide (1) a commercial inhibitor composition capable of use at start-up and for maintenance of passivity during normal operation and (2) a method for determining the appropriate times to add inhibitor.
These and other objects and advantages of the present invention will become apparent to those skilled in the art from the following description and claims.